The subject matter disclosed herein relates to an air cycle machine and, more particularly, to a strut plate assembly for an air cycle machine.
Conventional aircraft environmental control systems (ECSs) incorporate an air cycle machine, also referred to as an air cycle cooling machine, for use in cooling and dehumidifying air for an aircraft cabin. Such air cycle machines may include two or more wheels disposed at axially spaced intervals along a common shaft. The wheels are part of, for example, a compressor rotor, a turbine rotor, a fan rotor or an additional turbine rotor or an additional compressor rotor. In some cases the turbine or turbines drive both the compressor and the fan.
On aircraft powered by turbine engines, the air to be conditioned in the air cycle machine is typically compressed air bled from one or more of compressor stages of the turbine engine. In conventional systems, this bleed air passes through the air cycle machine compressor where it is further compressed. The compressed air is passed through a heat exchanger to cool the compressed air sufficiently to remove moisture and dehumidify the air. The dehumidified compressed air is expanded in the turbine of the air cycle machine to both extract energy from the compressed air so as to drive the shaft and also to cool the expanded turbine exhaust air before it is supplied to the aircraft cabin as conditioned cooling air.
A flow path of an air cycle machine can also include a heat exchanger cooling flow that draws air through the heat exchanger, past a fan rotor, and dumps the flow into an overboard duct. The fan rotor can be used to establish the flow when insufficient ram air is available to draw air through the heat exchanger. While in service, the heat exchanger can become partially clogged due to dust or other contaminants that reduce available flow volume to the fan rotor, which pushes the fan rotor closer to its surge limit. Designs that attempt to enhance flow as the fan rotor approaches its surge limit may experience a reduction in performance when operating under off-design conditions, which can reduce tolerance to heat exchanger blockage.